First or second focal plane????

Kino M

Kino M

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Staff member
Whats the skinny on the difference between the two and the advantages of each???? I have a Leupold scope (VX III 6.5X20 with the varmit recticle) that is "calibrated" but only works on like 17x?????? Why the heck then would they build a variable that did'nt work on ALL pwer settings????? Is this where the focal plne thingy comes into play??
 
kino,
FFP reticles get larger in accordance with your power settings.
get in touch with loopy and they should be able to give you explicit instructions on how to use the reticle to its fullest capability. like this say a mildot is calibrated to 20x setting, then on 10X each full dot is 2 mils. catshooter can tell you alot more than I could about scopes maybe he'll chime in
RR
 
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Whats the skinny on the difference between the two and the advantages of each???? I have a Leupold scope (VX III 6.5X20 with the varmint reticle) that is "calibrated" but only works on like 17x?????? Why the heck then would they build a variable that didn't work on ALL power settings?????



That is because as you change the magnification, the reticle stays the same, so the settings (distances) on the reticle can only be accurate at one setting.

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Is this where the focal plane thingy comes into play??



Yeah... this is "where the focal plane thingy comes in??"

In a First Focal Plane reticle, the reticle changes size the same as the target, so the spacing of the lines are always the same as their size on the target... you increase the power 3x, you increase the target size 3x, you increase the reticle 3x.

The down side is the reticle gets larger AND thicker as the power goes up, and it gets smaller and thinner as the power goes down - just the opposite of what you want.


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Mine matches up with common ballistics at 13X and 17X. I contacted Leupold to explain that their advertising was conveniently ambiguous about how that reticle works. Most folks aren't optics experts and therefore don't understand that it only "works" at two powers. No where in their literature does it say 13X or 17X. They talk about the big and small triangle which could be interpreted as a separate setting which would work thru all the powers. Like I said, most folks are not optics experts. All they would have had to say was works at two powers. Conveniently ambiguous. They probably did not intend to hide the limitation, just did not use a straight forward, simple explanation.
I requested the moa numbers for all the powers, and was told they didn't have them. Now, I find this very hard to believe. I attempted to measure the moa at 100 yards for all the powers but could not achieve enough accuracy. Still
working on the issue. Why not just publish the numbers?
For the math experts. Is this a straight line relationship?
If one would graph the 13 and 17 power moa's could you not determine the moa's of some other powers?
 
The main advantage of a FFP reticle is that it allows the shooter to range a target using reticle stadia regardless of scope magnification. Good for tactical applications where time is of the essence and quick thinking/shooting go hand in hand.

Bakerboy,
You can mess around with your SFP reticle at different mag settings to "fine tune" bullet drop according to your rifle & such. You may find that your particular ballistic reticle matches up with your rifle/load at a different power setting than what the factory recommends. Only experimenting will determine if this is true.

To measure the subtensions of particular ballistic reticle in MOA at different mag settings, the no nonsense way is to do what you did. Put a target up with a yard stick EXACTLY 100yds from your firing position. You can then determine "shooters" MOA of each corresponding drop stadia by simply measuring them against the inches on the yardstick.

This kind of stuff is fascinating if you can wade through the math part of it...
 
One of the guys over at Specialty Pistols website is getting the VHR reticle in the 6.5-20X also, and i think i've convinced him to measure the reticle also at 20X. It's supposed to be inversely proportional, but that's assuming the power ring is relatively accurate regarding magnification. I used to play around with calculating a particular subtension for a particular scope right out the front window of my house using measured signs at a lasered distance from my window. Most of the time most of the scopes were very close to calculated. I was also able to measure reticles along a sign post 98 yds. from the window (most sign posts have holes drilled in them at exactly 1" on centers). I've found the Thompson Targets with the red squares that r further didvided into .25 inch per hundred yd. provide the easiest method of measuring tho. Here's a link that should give u the most exact system of measuring (as far as i can tell). This copied from opticstalk.com--

http://opticstalk.com/forum_posts.asp?TID=8223

I still can't believe that Leupold didn't calibrate the reticle subtensions for the highest power though on that scope--crazy.

If u wish to adjust power (subtension) for the best trajectory fit (even ydgs.) here's something copied from SP site again that should be the simplest method of doing it (non-calculated)--

1) Establish the load u want to shoot, and record MV.

2) Run a ballistics program and manipulate the x-hair zero until u get the best (intuitive) trajectory to reticle fit possible. What this does is it simply establishes your best x-hair zero for that reticle.

3) Set tgts. at each distance that the stadia r supposed to be zeroed at according to the ballistics program.

4) Shoot the tgts. using only the main x-hair for a zero. U'll need some big tgts. as range increases (sometimes aiming at the top of them is a handy way to go).

5) Measure the distance between the x-hair bull on each tgt. and the group.

6) Convert that measurement to inch per hundred yds. Ex-- 35" low at 500 yds. would be 7 inch per hundred yds.

7) Go back to 100 yds. and put a black mk. on the tgt. for each range below the main x-hair bull. Ex-- put 1 at 7 inches below the bull for the 500 yd. reference.

8) Go back to the bench and adjust the power so it best matches the actual zeros, paying particular attention to the longer ranges as error at LR has a larger effect than short range.

9) Mark the scope somehow (might write it down too somewhere).

10) Now remeasure your windage stadia, and relaculate the windage system.

Now when out hunting all u'll need to think about is making sure u adjust the power correctly, and windage if it exists, since vertical compensation will be intuitive...once practiced.
 
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. Is this a straight line relationship?
If one would graph the 13 and 17 power moa's could you not determine the moa's of some other powers?



U know it's interesting that u should mention this, because it's sometimes amazing what can be accomplished with a SFP scope reticle--even simple plex. I was out coyote hunting with a friend's kid couple years ago. He brought along a little 22 Marlin that had a 3-9X Simmons rifle scope, and bipod. It really was a neat little setup this kid had. As we were walking back to the truck i asked him if i could look at it. The plex reticle looked like it subtended about 6 MOA to the lower post tip @ 9X. So i thought if he adjusted it to 3X that would give him about 18 MOA to use for a long-range zero--maybe 300 yds. or so. We got setup in a pr. dog town we had to walk thru to get back, and i lasered a couple pr. dogs on top of a mound at about 290-some yds. This kid sets up and shoots while i spot. The 1st shot was just low on the mound (no wind, mind u). The kid compensates a little and nails this dog and he falls off the back of the mound. The dog scurries back up to the top of the hole and this kid nails him again and kills him. The other dog gets on top of the mound and the kid nails that 1 also. We couldn't believe it when we got to the mound and there's 2 full-grown dogs laying on the backside dead. All this @ 3X too. Zeroing a SFP scope for other than the scope's highest power does work, and sometimes some amazing things can happen when u use math in the field.
 
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Mine matches up with common ballistics at 13X and 17X. No where in their literature does it say 13X or 17X. All they would have had to say was works at two powers. "Conveniently ambiguous" (???).

They probably did not intend to hide the limitation, just did not use a straight forward, simple explanation.



There is no such thing as "common ballistics" - every cartridge is different, and has different intersection points at 200, 300, 400, and 500.

And both 13x AND 17x won't match any cartridge... common or otherwise. If you are lucky, one power will match the cartridge you are shooting, but it will happen at only one power... and that might NOT be the power with the little triangle.

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I requested the moa numbers for all the powers, and was told they didn't have them. Now, I find this very hard to believe.



They DON'T - "they", the guy or gal that spoke to you on the phone was a "phone person", not an engineer. They have a list of Frequently Asked Questions (FAQ's), and if the answer isn't on the list, they don't have the information...

... but you need to do a little work yourself - just divide the magnifications by what you know, and you will get the ones that you don't know. Don't expect the "phone person" to do it for you.

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I attempted to measure the moa at 100 yards for all the powers but could not achieve enough accuracy. Still
working on the issue. Why not just publish the numbers?



Cuz you need to do it yourself - they can't publish EVERY answer to every possible question, in advance.

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For the math experts. Is this a straight line relationship? If one would graph the 13 and 17 power moa's could you not determine the moa's of some other powers?



Of course you can...

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I still can't believe that Leupold didn't calibrate the reticle subtensions for the highest power though on that scope--crazy.



It's because they use the same reticle for many scopes, so they can't have it be for the maximum power for each, cuz they don't have the same maximum power... and not all people use maximum power to shoot - medium power is a necessary compromise.


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Don't trust the Leupold power ring calibration. The range estimating system is not correct in my scope. The subtension should be linear with power increase, and it isn't according to the power marks in my VX-III.

1 nice thing about the Nikon system is that they provide all the reticle subtensions at lowest, calibrated, and highest powers.

IMO, a 2FP ballistic reticle subtension should be calibrated or designed for the scope's highest power. I haven't seen too many guys yet that thought the 6.5-20X VHR was set up right. It's not the 1st mistake i've seen Leupold make. Though i still believe their products r excellent. The Burris BMD is set up the same way on their higher-powered scopes.
 
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I am used to a Shepherd Scope which do not change so this is new to me but here is the things I have learned. I am waiting on my Scope to arrive so I do not actually have it in my hands yet. I have a Leupold 3X9X50 VII that I sent back to Leupold to have the ballistic reticle put in as well as the Ranging System and the various Light Filters.

1. Using MAX Power zero at 200 (This is what Leupold recommends) I think actually shooting from 200 is best.

2. After Zeroing move to 5 or 6 hundred (what ever is the Max range) and make your rifle hit by zooming your scope. Mark this setting as the setting that works with your load and rifle. The Reticles should now work for closer shots.

3. The Light filters will only work with newer Leupold scopes because the older ones like mine do not have threaded Objective Housings. Leupold will convert them for you for a fee.

4. Any variable Scope can be a Range Finder, just find a known size Object and mark where it fits at known ranges.
 
FFP's are not a bad thing except for long range shooting. The problem is small targets are covered up as the reticle gets bigger when you zoom up. Schmidt& Benders are the best glass out there but they have ret's that are too big for longrange work on small targets. You can have the new 5-25 model in a 2nd focal plane with a small ret but have not seen this one yet. The new 12-50 ought to be interesting.
 
This is all VERY confusing! Thank GOD I just shoot a scope that just has one up, and one across, and I just try to get it in there somewhere.

Once in awhile I get LUCKY!! /ubbthreads/images/graemlins/laugh.gif
 
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